Various aspects of the present disclosure may relate to base station antennas, and, more particularly, to dipole antenna elements of base station antennas.
Multi-band antennas for wireless voice and data communications are known. For example, common frequency bands for Global System for Mobile Communications (GSM) services may include GSM 900 and GSM 1800. A low band of frequencies in a multi-band antenna may include a GSM 900 band, which may operate in frequency range of 880-960 MHz. The low band may also include additional spectrum, e.g., in a frequency range of 790-862 MHz.
A high band of a multi-band antenna may include a GSM 1800 band, which may operate in a frequency range of 1710-1880 MHz. A high band may also include, for example, the Universal Mobile Telecommunications System (UMTS) band, which may operate in a frequency range of 1920-2170 MHz. Additional bands may comprise Long Term Evolution (LTE), which may operate in a frequency range of 2.5-2.7 GHz, and WiMax, which may operate in a frequency range of 3.4-3.8 GHz.
When a dipole element is employed as a radiating element, it may be common to design the dipole so that its first resonant frequency is in a desired frequency band. In multi-band antennas, radiation patterns for a higher frequency band may become distorted by resonances that develop in radiating patterns that are designed to radiate at a lower frequency band. Such resonances may affect the performance of high-band radiating elements and/or the low-band radiating elements of the multi-band antenna.